Effects Of Exogenous Melatonin On Seed Germination And Seedling Physiological Characteristics Of Bromus Inermis Under Drought Stress

In this study,the effect of melatonin（MT）immersion on seed germination of Bromus inermis under drought stress was investigated using Bromus inermis cv.Wusu No.1 as experimental material,and the appropriate MT immersion concentration and duration for promoting seed germination of Bromus inermis under drought stress were screened.The effects of spraying exogenous MT on chlorophyll content,Pro content,RWC content,MDA content,RC content,SOD activity,POD activity and CAT activity of Bromus inermis seedlings under drought stress were investigated to explore the role of exogenous MT in alleviating drought stress damage in Bromus inermis,and to screen the appropriate MT spraying concentration to provide a reference method for MT application in production practice.The main findings are as follows:（1）Drought stress significantly inhibited the seeding length and radicle length of Bromus inermis seeds.The seeding and radicle length of Bromus inermis seeds treated with MT immersion were elongated under drought stress,with the maximum germ length of 6.29 cm in Bromus inermis seeds treated with 50μmol·L^-1MT immersion for 12 h.The significant growth of Bromus inermis radicle was 6.47 cm under 25μmol·L^-1MT immersion treatment for 48 h.（2）Drought stress significantly reduced the germination potential,germination rate,germination index and vigor index of Bromus inermis seeds.Improved germination of Bromus inermis seeds under drought stress after MT immersion treatment,The affiliation function analysis yielded the highest germination power of Bromus inermis seeds when immersed with 75μmol·L^-1MT for 24h.At this time,the germination rate,germination potential,germination index,vigor index,seeding length and radicle length of the tested materials increased by 34.24%,68.71%,69.61%,78.14%,5.82%and 20.38%respectively,compared with the 0μmol·L^-1MT seed immersion group.（3）The chlorophyll content and RWC of Bromus inermis seedlings decreased,while Pro content,MDA content and RC increased,and SOD,POD and CAT activities enhanced under drought stress.Spraying MT could alleviate the decreasing trend of chlorophyll content and RWC in Bromus inermis leaves under drought stress to varying degrees,and could reduce MDA content and RC,increase SOD,POD and CAT activities,and further increase Pro content in leaves under drought stress.（4）The affiliation function analysis yielded that when the soil water content reached 60%of the field holding capacity,the spraying of exogenous MT had no significant effect on the physiological characteristics of Bromus inermis seedlings;when the soil water content decreased to 40%of the field holding capacity,the spraying of 100μmol·L^-1exogenous MT had the best effect on the mitigation of drought stress for Bromus inermis seedlings;when the soil water content decreased to 20%of the field holding capacity,the spraying concentration of exogenous MT increased to 200μmol·L^-1had the best effect on the mitigation of Bromus inermis seedlings under drought stress conditions.